It's a failure to read the manual thing. Every OTR microwave ever manufactured functions as a hood by definition, and basically all of them (I can only think of like two exceptions) have the option to be configured for either recirculation or to duct outside. It's just that most models come out of the box already configured for recirculation and most people ('s contractors) are so averse to reading that they fail to realize you can flip the blower motor over and thus cause it to actually accomplish something (provided a duct is in place) rather than just blowing stale air back in your face.

[–] Waraugh@lemmy.dbzer0.com 2 points 3 hours ago (1 children)

The ducting behind a microwave is not that common in my experience. It makes sense for microwaves to come preconfigured to recirculate instead of trying to exhaust to a sheet of drywall because most people are going to install it how it comes out of the box. I’ve installed dozens of microwaves and only twice has ducting existed to flip the venting for. Higher end houses typically have dedicated exhaust fans and lower end houses never seem to have ducting for a microwave. I installed a dedicated fan that exhausts out the roof at my house. Even with ducting those microwave exhaust fans barely provide anything of value. I’m sure my experience is very regional but it seems like a really niche middle ground where someone would bother venting out of the kitchen but also not care enough to have a purpose built exhaust fan.

[–] dual_sport_dork@lemmy.world 1 points 3 hours ago* (last edited 3 hours ago) (1 children)

Part of the problem there is I have guys just absolutely insist at me that a microwave "can't" be vented outside so they don't bother to install a duct, and tell me that in order to vent outside you "have" to get a hood instead. This is obviously bogus.

This also leads to the inevitable Contractor Special where a duct was there, often when the user is replacing an old hood with a microwave, but the installer just shrugs and slaps the microwave on the wall as-is where A) it is inevitably too tall and now way too close to the stovetop, and B) covering the duct outlet while still recirculating back into the room. Whenever I unearth one of these in my travels it makes me want to track down whoever the hell installed it and then punch them so hard they come clean out of their socks.

People are for some reason hyperfixated on getting appliances off of their countertops, which is why the over-the-range microwaves became so prevalent in the first place. (And then they all immediately filled the spot where their countertop microwave used to be with a countertop air fryer instead, but that's a whole different discussion.)

[–] Waraugh@lemmy.dbzer0.com 2 points 3 hours ago* (last edited 3 hours ago)

Yeah that would drive me insane to run across. It’s not even particularly hard to tell that the exhaust fan motor is reversible just by looking at the top/back of the microwave before it is installed. Every one I’ve seen looks pretty damn modular in comparison to the rest of the microwave shell.

Edit: reversible is the wrong word, able to be unscrewed and rotated, I’m sure you know what I meant but on a reread of my comment I wanted to clarify.